Salisbury Steak Garlic Mashed Potatoes Mushroom & Onion gravy

For the Steaks:
1/3 cup breadcrumbs
1 egg
1 small yellow onion grated
1 teaspoon kosher salt
1/2 teaspoon black pepper
1 lb. lean ground beef such as 90/10
1 tablespoon extra-virgin olive oil
For the Mushroom Gravy:
2 tablespoons butter
8 oz. sliced mushrooms I used baby portobellas (cremini)
2 tablespoons all-purpose flour
2 cups beef broth
Kosher salt to taste
Black pepper to taste
Instructions:

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